Bringing this one back from the dead. I live in the PNW where annual rain is measured in feet, and the RH is typically 85%+. My reloading room is in the garage where the room temps are subject to the season, so I do dehydrate to keep the powder consistent.
I use a 9-tray Excalibur food dehydrator that sits on the bench. I keep a couple glass 2-cup Pyrex measuring cups inside that I dry the powder in. I dry it for 90 minutes - that gives me time to get brass prepped and primed prior to throwing powder. In my data, it's has made the biggest difference in controlling consistency across all loads, I use less powder getting to optimum accuracy nodes, and experience lower pressure with higher velocities.